The invention generally relates to backlight systems, and more particularly to backlight systems for mobile display systems.
Mobile devices, such as mobile and handheld PCs, portable TVs and other mobile Internet appliances, have been widely used in our daily lives. Due to their size and mobility, these devices are particularly convenient to people who travel frequently or need to have access to information at any time or in any location, from the Internet or in a stored database for example. When the AC power is available, mobile devices are typically used in conjunction with a docking station on a desktop or elsewhere in an attached or docked mode. The docking station provides network connections as well as connections to peripheral devices, such as a printer. Because their flexibility of being able to be used in either docked mode or mobile (or undocked) mode, there are requirements for high brightness (with similar luminance as stationary monitors) when the mobile devices are docked and powered by mains power, and for optimization of battery life when they are operated in the mobile mode.
A conventional solution for notebook PCs for example, is to use a dimmable power supply. In this case, the backlight power is regulated based on the condition of the re-charger being attached to the notebook PC. When the notebook PC is used in the mobile mode, the optimization of battery life can be achieved by reduction of power in the backlight. This consequently results in reduction of luminance to 60-80 candela/m2. If the notebook PC is plugged into an AC power outlet on the wall, the maximum power of the backlight is increased by increasing the current of the internal lamp or the current duty cycle, relative to its maximum value in the battery operated mode. However, even with the increase of the current the brightness achieved is only in the range of 80-100 candela/m2, which is far less bright as compared to that of flat panel monitors powered mains power, which has the luminous intensity of 250 plus candela/m2.
Thus, most mobile electronic products today are not able to achieve high brightness, unless both weight and thickness are sacrificed.
Therefore, there is a need for a mobile device that maintains mobile characteristics of low weight, thinness and long battery life, while providing functionality, e.g., high brightness, of a mains powered desktop product.
The present invention provides a mobile display system with an improved backlight system. According to a first embodiment of the invention, the mobile display system comprises a mobile unit including a flat panel display, and a first backlight circuit for providing light to the display. The first backlight circuit includes a plurality of lights sources disposed near edges of the mobile unit and a single power supply for powering a pre-selected one of the light sources. The system also comprises a base station capable of being powered by an external power source. The base station includes a second backlight circuit that comprises at least one power supply for powering the plurality of light sources in the mobile unit when the mobile unit is attached to the base station. This embodiment allows the use of a single power supply in the mobile unit, keeping weight and power consumption low, but allowing long battery life at the compromise of display surface light intensity.
According to a second embodiment of the invention, the mobile display system comprises a mobile unit including a flat panel display, and a first backlight circuit for providing light to the display. The flat panel display has selected surfaces made in materials capable of coupling external light. The first backlight circuit includes a single light source disposed near a pre-selected edge of the mobile unit and a single power supply for powering the light source. The system also comprises a base station capable of being powered by an external power source. The base station includes a second backlight circuit that comprises a plurality of light sources disposed near edges of the base station and at least one power supply for powering the plurality of light sources. The base station has selected surfaces made of materials capable of coupling light out of the plurality of light sources and into the display when the mobile unit is attached to the base station. This embodiment allows the use of a single power supply and a single light source in the mobile unit, keeping weight and power consumption low, but allowing long battery life at the compromise of display surface light intensity.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.